Interdisciplinary Team Locates Sunken Plane

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A week apart this year, MIT Tech Talk reported on two events: the ditching at sea of a plane by Dr. William J. Dally, associate professor of electrical engineering and computer science (MIT Tech Talk, Sept. 30), and the publication of a humorous book about seasickness by Charles H. Mazel, a research engineer in the Department of Ocean Engineering and lecturer in the Edgerton Center (MIT Tech Talk, Oct. 7).

Oddly enough, the two got together this fall to find and recover the plane.

It's an interesting yarn-it even led to the rescue of four lobsters-and, because Dr. Mazel is an author, we invited him to tell the story..

By Charles Mazel

Ocean Engineering

When MIT Tech Talk last dealt with William Dally's Cessna 210 airplane, it was lying on the bottom of Long Island Sound, just outside of New London, CT. On August 9, Dr. Dally was forced to ditch in the ocean after his engine failed; he managed to climb out of the cockpit before the plane sank, and was in the water for an hour before he was rescued. The story said the airplane would be left beneath the sea.

As time passed Professor Dally decided that he wanted two things out of the wreckage: his pilot logbook and an answer as to why his engine failed two flying hours after a propeller overhaul. He learned of me through my brother-in-law Professor Gerald J. Sussman, a colleague in his department.

I was experienced in running searches of this type, having learned side-scan sonar operation from Doc Edgerton [the late Harold E. Edgerton] and also having worked for Klein Associates, a sonar manufacturer, for five years.

A team was assembled, and on Saturday, Nov. 14, six people left the Kresge parking lot at 6am to drive to New London. I was assisted in organizing and running the operation by Noah Eckhouse, a research specialist in the ocean engineering department. Professor Dally was there to operate the navigation system. Ocean engineering graduate students Shane Merz and Don Atwood came along to observe the operation, learn about sonar, and help with equipment and boat handling. In keeping with the Edgerton Center's goal of offering interesting hands-on educational experiences to undergraduates, aero/astro junior Jim Cox was also recruited for the team.

The group installed the sonar and navigation equipment on a rented 34-foot vessel named Patience. We used a Klein Associates 500 kHz high resolution side-scan sonar which is on loan to the Sea Grant Program.

The sonar allowed the team to view the underwater terrain at a range of up to 100 meters on either side of the towfish, the torpedo-shaped unit containing the sonar transducers that is towed by the boat.

Professor Dally had an estimated position for the crash site based on his line of approach to Groton Airport, where he was trying to land after realizing he had engine trouble, and a navigation fix he took when he came out of the clouds at an altitude of 400 feet. Based on this estimate, he had marked out a search area allowing for a margin of error. A Global Positioning System (GPS) receiver was used to guide the boat along the search lines, which were spaced 100 yards apart.

The bottom was smooth, and the sonar showed the location of objects as small as lobster traps. After just over an hour of searching, the plane was located at one of the extreme corners of the area, two miles out to sea and about a half mile from Professor Dally's estimate.

The side-scan sonar record showed that the airplane was largely intact, lying in 45 feet of water with the starboard wing resting on the sea floor.

After precisely determining the position Eckhouse and I put on SCUBA gear and swam down to the airplane. We found that the fuselage was bent just forward of the tail, the starboard wingtip was broken off, and most of the aluminum skin was separating from its supporting structure. The interior of the plane was filled with sediment and rotting pieces of seats and carpet.

We were able to open the pilot-side cockpit door and

the luggage door and recover a number of items, including Professor Dally's logbook and his Macintosh PowerBook (laptop computer). While the information in the logbook was salvageable, the same could not be said for the PowerBook after its three-month salt-water bath.

We also found that the plane's tail was resting on a lobster pot, pinning it to the bottom with four live lobsters inside. There was no buoy line to the surface, so we cut the netting to free the lobsters.

Before leaving the bottom, we tied off a marker buoy to the plane's propeller to guide salvage divers directly to the wreckage. The next day, the salvors successfully lifted the plane from the bottom and brought it ashore. Three days later, a mechanic from the National Transportation Safety Board tore down the plane's engine and found out that the failure had nothing to do with the propeller work. A crankshaft bearing had spun in its seat, and the resulting internal engine wear clogged the oil holes with aluminum shavings, causing the engine to seize from oil deprivation. Just one of those things.